Seawalls are commonly built along shorelines to protect the adjoining ground from erosion and to provide an aesthetic appearance to the shoreline. Seawalls typically extend downwardly into the solid bottom of the waterway and extend upwardly a short distance above ground level. Seawalls are made of various materials including poured concrete, masonry blocks, steel or plastic panels, and the like. The term “seawall” is used herein to include retaining walls, bulkheads, sheet pilings and other erosion control barriers between land and water.
When it rains or when waves overlap the seawall, water enters the ground behind the seawall and causes it to expand. The expansion of the ground creates hydraulic pressure that exerts a considerable outward force on the seawall. Without a mechanism for relieving the hydraulic pressure, the seawall can be damaged.
A common mechanism for relieving hydraulic pressure is to include drain holes (sometimes known as weep holes) at spaced intervals along the seawall. The holes are located above the water level and below the ground level. The holes provide a path for water in the ground to pass through the seawall and empty into the waterway. A simple hole in the seawall provides some drainage for water, but also allows excessive amounts of soil to escape. To allow water to escape but to retain soil, seawall drain holes preferably contain a filter. The term “filter” is used herein to refer to a filter assembly or to the replaceable filter element itself, as the context requires. When the meaning may not be clear, the terms “filter assembly” or “filter element” are used.
As with all filters, seawall drain filters must be cleaned periodically. When the filter is placed underground on the inner (landward) side of the seawall, digging is required to gain access to the filter.
Gentry, U.S. Pat. No. 6,394,706, May 28, 2002, discloses a seawall filter assembly with a filter element that is changed from the outer (seaward) side of the wall, thus eliminating the need to dig into the ground. The seawall filter assembly contains a conduit that is driven into a hole in the seawall. The inner (landward) end of the conduit contains a disc filter element. The outer (seaward) end of the conduit extends outwardly from the seawall. This seawall filter assembly suffers from several disadvantages. First, it is difficult to drive the conduit into the hole. Second, a special tool is needed to install and service the filter element. Third, the filter element has a surface area of filtration equal only to the cross-sectional area of the inside of the conduit. As a result, the filter element must be replaced frequently. And fourth, the conduit extending outwardly from the seawall can damage boats that dock along the seawall and is, itself, prone to damage.
Accordingly, there is a demand for an improved seawall filter. More particularly, there is a demand for a seawall filter that is easier to install, easier to service, has a much greater surface area of filtration, and is flush with the outer surface of the seawall.